ORP with and without UV

[Thor2j]

Somebody who understands this way better then me please explain. Usually run my UV 24/7. With UV on my ORP fluctuates 370-400. I turned my UV off and now ORP is 260-285 . Why the difference?

Thanks

 

[taricha]

There are a lot of compounds that are oxidized by UV.
Organic compounds, particularly those responsible for yellow water are oxidized by high energy light, especially UV. There are also metals that are photo-oxidized. The end result is that with more compounds oxidized, we can expect ORP to go up.

 

[Thor2j]

Thanks!!